Tubular components or articles, such as pneumatic tire body plies have previously generally been built by utilizing woven fabric and calendering same with rubber stock which, when cut to size, entails wrapping the sheet component around a tire building drum and overlapping the ends of the sheet to produce an annulus with a generally axially extending seam. Such a seam is generally disadvantageous in that the discontinuity in the now annular component may produce not only weak spots, but also an asymmetrical construction tending to cause a force unbalance in the completed tire.
In order to avoid this lapped or seamed construction, extrusion has been employed in the prior art in the case of knit tubular fabric and annular seamless elastomeric tubes having reinforcement cords therein disposed generally longitudinally of the tube during extrusion. However, these attempts have not been commercially successful since there was insufficient control in terms of the placement and spacing of the cords to obtain the desired high performance required in modern engineered constructions.
The prior art has not successfully addressed a coextrusion apparatus and method to produce an article having a circular array of small diameter cords of a very large number (500-2,500) cords in a thin walled (0.070 inches) annular tubing ranging up to 16 inches or more in diameter. In tire construction, for example, the uniformity of spacing of the reinforcing cords of the body ply is crucial to the subsequent tire building steps, and uniformity of expansion is a direct result of uniform spacing of the reinforcement cords.
U.S. Pat. Nos. 2,874,411 and 3,183,135, both to Berquist, disclose an apparatus and method, respectively, for manufacturing a tire. FIG. 4 of the former discloses individual strands, from a bank of spools, passing into an annular guiding aperture of a die head and passing out through an annular aperture in an exit sleeve. A mandrel supports the strands and causes the plastic, supplied by a single extruder, to form a tubular structure in which the strands are parallel. A floating mandrel is utilized and seeks its own location in the outlet and center of the tubular structure so as to prevent the tube from collapsing under the pressure of the plastic. The method of U.S. Pat. No. 3,183,135 includes forming a hollow circumferentially endless cylinder by extruding parallel strands, substantially longitudinal of a floating mandrel, while simultaneously coating and bridging the strands with an adhesive insulating coating, using the apparatus of U.S. Pat. No. 2,874,411.
U.S. Pat. No. 3,615,987 to Blatz is directed to a method of extruding continuous annular seamless components of rubber material, containing reinforcement filaments embedded therein, comprising the steps of extruding a tube of this material, cutting the extruded tube into predetermined lengths, and positioning the lengths onto a tire building drum. The extrusion apparatus includes an extrusion head having a nozzle mounted partly within the outlet of the extrusion head so that the interior surfaces of the nozzle and the extrusion head together form a smooth frustoconical surface which diverges in the direction of the flow of the material being extruded. A conical form core, disposed within the extrusion head outlet portion and the nozzle, is axially movable therein, thus causing gradual consolidation of the extruded material. A plurality of substantially radially extending ceramic inserts is arranged on the periphery of the nozzle and communicates with the passage between the core and the nozzle, with these inserts serving as the inlets for the reinforcing cords. However, the cords are forced to undergo a 90.degree. transition upon entering the single annular stream extrudate.
U.S. Pat. No. 4,283,241 to Hollmann discloses a method and apparatus for preparing carcass plies for radial tires wherein the apparatus includes extruding means including a plurality of nozzles for separately extruding, from each nozzle, a strand of vulcanizable rubber composition, wherein the nozzles are arranged to extrude a plurality of strands in a tubular array. Elongated reinforcing members are fed to the nozzles respectively for discharging therefrom respective reinforcing members individually coated with the rubber composition. However, textile machinery means are utilized for winding the coated strands with relatively weak transfer circumferential strands. It appears that but a single extruder is utilized.
U.S. Pat. No. 4,484,966 to Kawamoto discloses a process of manufacturing carcass bands which are reinforced by cords and are employed in fabricating a radial tire. This process includes the steps of unwinding the plurality of cords from a plurality of reels, traveling the cords through apertures formed in guide members and entering a rubber coating mechanism and thereafter coating the cords with rubber material by means of the rubber coating mechanism to produce a continuous cylindrical tube having cords embedded therein. A pair of controlled rollers, upstream from the coating mechanism, is utilized for maintaining the cords even in tension and to prevent their twisting. A plurality of guide members, immediately upstream of the coating mechanism, guides the cords prior to entering the passageways within the rubber coating mechanism. Again, only a single hollow stream of elastomeric material is utilized.
U.S. Pat. No. 4,050,867 to Ferrentino et al. discloses an extrusion head for extruding elastomeric material on at least two filaments having a diameter on the order of 0.1 mm and having a high modulus of elasticity while maintaining a constant spacing therebetween. The nature of the cord guides illustrated in the patent is not adequate to control a large number of textile cords and prevent entanglement. U.S. Pat. No. 4,132,756, also to Ferrentino et al. and a division of U.S. Pat. No. 4,050,867, is cited for its disclosure of an extrusion process wherein the five filaments (F and W) are subjected to mechanical tension applied from the outside of the extrusion head in any conventional manner, thereby providing a cable with a constant spacing between the filaments.
U.S. Pat. No. 4,150,929 to Brandt pertains to the preparation of miniature ribbon cables having up to 100 fine conductor wires of a diameter of 0.010 to 0.015 inches. The gauge of the extrudate of the present invention must be controlled within a few mils whereas the adjustment of the die position of Brandt, via rocking set screws 53 and 54, is inadequate to control the gage over the large circumferential dimension characteristic of the present composite tire component. While Brandt's quills 37 are formed of thin-walled material, such as hypodermic needle stock, their delivery ends are swaged down to reduce the internal diameter to a dimension close to the external diameter of the wires. Swaged ends, as those in Brandt, would require replacement if elastomeric material backs into the flow tube should a cord break. In the apparatus of the present invention, not only is the backflow slight, but if a reinforcing element break is detected while running, rethreading can even be accomplished under operating conditions.
U.S. Pat. No. 3,697,209 to Schiesser discloses an apparatus for manufacturing reinforced tubings from plastic materials wherein a first inner layer of the tubing wall is continuously extruded, in an extruder head, over a guide serving to form the cavity of the tubing whereinafter strand-like reinforcing material is continuously applied in a longitudinal direction of the tubing on the outer surface of this inner layer which is thereafter coated by at least one further or outer layer of a plastic substance. The apparatus and method of Schiesser differ, among other things, from the present invention in that the latter introduces the reinforcing elements into the interface of two merging circumferentially continuous concentric streams.